This application is based on Japanese Patent Application No. 11-26158 filed Feb. 3, 1999, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an electrically controlled braking system including a brake control apparatus which is adapted to control a brake by controlling an electric energy supplied thereto from an electric power source.
2. Discussion of the Related Art
JP-A-5-158742 discloses an example of such an electrically controlled braking system including a brake for braking a wheel of an automotive vehicle, an electric power source, and a brake control apparatus for controlling the brake by controlling an electric energy supplied thereto from the electric power source. The brake is actuated by a pressurized working fluid, and the brake control apparatus includes a solenoid-operated valve device, and a control portion constituted principally by a computer, which is adapted to control an electric energy to be supplied to a solenoid coil of the solenoid-operated valve device so that an operation of the brake is controlled.
In the electrically controlled braking system, an electric power source switch is provided between the electric power source and the solenoid-operated valve device. This electric power source switch is turned from an OFF state to an ON state when an ignition switch of the vehicle is turned on. Therefore, this electrically controlled braking system suffers from a problem that the brake is not activated by an operation of a brake operating member while the ignition switch is off. Accordingly, the braking system is necessarily arranged such that a manually operated brake is activated while the ignition switch is in the off state. This arrangement suffers from another problem that the braking force produced by the brake changes when the ignition switch is turned on or off while the brake operating member is placed in an operated position. If the ignition switch is turned from its ON state to its OFF state while the brake operating member is placed in an operated position, the electrically controlled braking system changes from an operated state to a non-operated state, causing a change in the braking force, which may make the vehicle operator feel uneasy about the braking system. Further, the solenoid-operated valve device may be inoperable in the case of an excessive drop of the output of the single electric power source, or in the event of occurrence of any abnormality of an electric circuit connecting the solenoid-operated valve device and the electric power source.
It is therefore an object to provide an improved electrically controlled braking system.
This object may be achieved according to any one of the following modes of the present invention, each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate and clarify possible combinations of elements or technical features. It is to be understood that the present invention is not limited to the technical features or any combinations thereof which will be described for illustrative purpose only. The term xe2x80x9celectrically controlled braking systemxe2x80x9d is interpreted to mean not only a braking system of the type described above, but also a braking system of a type wherein the brake includes an electrically operated actuator adapted to force a friction member onto a rotor so that the wheel rotating with the rotor is braked, while the brake control apparatus includes an actuator control device for controlling the electric energy to be supplied to the electrically operated actuator from the electric power source device, so as to control an operation of the brake.
(1) An electrically controlled braking system including an electrically controlled brake for braking a wheel of an automotive vehicle, an electric power source device, a brake operating member, and a brake control apparatus for controlling an electric energy to be supplied from the electric power source device to the brake, for thereby controlling an operation of the brake, when the brake operating member is operated, and wherein a switching device is disposed between the electric power source device and the brake control apparatus, the switching device being turned on for connecting the electric power source device to the brake control apparatus, in response to an operation of the brake operating member.
In the electrically braking system according to the above mode of this invention, the switching device disposed between the electric power source device and the brake control apparatus is switched from its off state to its on state when the brake operating member is operated, so that the electric power source device is electrically connected to the brake control apparatus, whereby the brake control apparatus is made operable to control the electrically controlled brake. Thus, the electrically controlled braking system does not require a manually operated brake which is adapted to be activated when the brake operating member is operated while an ignition switch provided on the vehicle is off. Further, the braking force produced by the brake will not change even when the ignition switch is turned on while the brake operating member is in operation. In other words, this arrangement prevents an undesirable change in the braking force. The switching device may be considered to be a power source switching device as distinguished from an actuator switching device and a controller switching device which will be described.
The brake control apparatus, which is provided for controlling an operation of the electrically controlled brake, may be adapted to control the amount of an electric energy to be supplied to the brake. When the amount of supply of the electric energy is zero or zeroed, the brake is at rest or de-activated. Alternatively, the brake control apparatus may be adapted to control the duty cycle of an electric actuator (e.g., electric motor) for operating the brake, namely, to alternately turn on and off the electric actuator so as to control a ratio of an ON period during which a predetermined amount of electric energy is supplied to the actuator, to an entire cycle time which is a sum of the ON period and an OFF period during which the electric energy is not supplied to the actuator.
(2) An electrically controlled braking system according to the above mode (1), wherein the electrically controlled brake includes a rotor rotating with the wheel, a friction member, and an electric motor for forcing the friction member onto the rotor, and the brake control apparatus includes a motor control device for controlling the electric energy to be supplied from the electric power source device to the electric motor.
In the braking system according to the above mode (2), which is a preferred form of the invention, an electrically operated actuator in the form of an electric motor is controlled by the brake control apparatus. Therefore, the present braking system is considered to be an electrically operated electrically controlled braking system. Where the electrically controlled brake includes a hydraulically operated actuator rather than an electrically operated actuator, it is comparatively easy to activate a manually operated brake in the event of an electrical failure of the electrically controlled braking system, or to selectively activate the manually operated brake or the electrically controlled brake. Where the electrically controlled braking system is an electrically operated braking system including an electrically operated actuator, it is comparatively difficult to activate the manually operated brake in the event of an electrical failure of the braking system, or selectively activate the manually operated brake or the electrically controlled brake. In this respect, the switching device provided according to the principle of this invention is particularly effective in the electrically operated braking system.
(3) An electrically controlled braking system according to the above mode (1) or (2), wherein the electrically controlled brake includes a rotor rotating with the wheel, a friction member, and an electrically operated actuator for forcing the friction member on to the rotor, the switching device is disposed between the electric power source device and the actuator.
In the braking system according to the above mode (3), the brake control apparatus may include an actuator control device which is adapted to control the electrically operated actuator and connected to the electric power source device such that the actuator control device and the actuator are connected in parallel with each other. In this case, the switching device is disposed between the electric power source device and the parallel connection of the actuator control device and the actuator.
(4) An electrically controlled braking system according to the above mode (1) or (2), wherein the electrically controlled brake includes a rotor rotating with the wheel, a friction member, and an electrically operated actuator for forcing the friction member onto the rotor, the braking system further comprising another switching device disposed between the electric power source device and the actuator, the another switching device being turned on to connect the electric power source device to the actuator in response to an operation of the brake operating member.
(5) An electrically controlled braking system according to any one of the above modes (1)-(4), wherein the switching device includes a plurality of switches connected in series with each other.
In the braking system according to the above mode (5) wherein the switching device includes two or more switches connected in series with each other, the switching device can be turned off as long as at least one of the switches can be turned off, even if some of the switches cannot be turned off for some reason or other. This arrangement makes it possible to prevent a problem that the electric energy is kept supplied to the brake control apparatus or the electrically operated actuator provided in the above mode (3) or (4).
The above arrangement is equally applicable to not only the switching device which is adapted to be turned off in response to an operation of the brake operating member, such as the switching device in the above modes (1) and (3) disposed between the electric power source device and the brake control apparatus, and the switching device in the above mode (4) disposed between the electric power source device and the electrically operated actuator, but also to other switching devices such as a switching device which is adapted to be turned off in response to an operation of an ignition switch provided on the vehicle, a plurality of actuator switching devices provided for respective electrically operated actuators such as electric motors, and a controller switching device which is turned on or off depending upon whether the brake control device is normal or abnormal.
(6) An electrically controlled braking system according to any one of the above modes (1)-(5), wherein the brake control apparatus includes a plurality of control devices each of which is principally constituted by a computer, and the electric power source device includes a plurality of electric power sources corresponding to the plurality of control devices, respectively.
In the braking system according to the above mode (6) wherein a plurality of sets of control devices and electric power sources are provided, the operation of the electrically controlled brake can be controlled by at least one of the control devices which is normally operable, as long as the corresponding at least one of the electric power sources is normal, even if the other electric power source or sources is/are abnormal.
(7) An electrically controlled braking system according to the above mode (6), wherein the plurality of control devices are substantially identical with each other.
The plurality of control devices are considered to be substantially identical with each other, if control commands generated by the plurality of control devices permit the electric energy to be controlled so as to establish substantially identical operating conditions of the electrically controlled brake. In other words, the control devices which are substantially identical with each other generate substantially identical control commands. Described more specifically, substantially identical operating conditions of the brake can be established if control commands generated by the respective control devices on the basis of the same input data are substantially identical with each other. That is, the control devices are substantially identical with each other where stored control programs executed by the respective control devices are identical with each other, or where the control devices employ the same hardware circuits. The control commands generated by the respective control devices may be substantially identical with each other even where the input data received by the control devices are more or less different from each other. Further, control commands generated by some of the control devices on the basis of a relatively large number of input data items may be substantially identical with control commands generated by the other control devices on the basis of a relatively smaller number of input data items, so that the operating condition of the brake as controlled by the above-indicated some of the control devices does not greatly differ from the operating condition as controlled by the other control devices. The control commands based on the relatively large number of input data items permit an intricate or fine control of the brake, while the control commands based on the relatively small number of input data items permits only a rough or coarse control of the brake.
(8) An electrically controlled braking system according to the above mode (6) or (7), wherein the brake control apparatus (18) includes a control on/off device for continuing a control of the electrically controlled braking system when predetermined at least one of the plurality of control devices is normal, and stopping the control of the electrically controlled braking system when the predetermined at least one of the plurality control devices is not normal.
In the braking system wherein the brake control apparatus includes a plurality of control devices, the operating condition of the electrically controlled brake can be continuously controlled even if some of the control devices are abnormal, as long as at least one of the control devices is normally functioning. When the predetermined at least one of the control devices is not normal, it is desired or required that the control of the brake be terminated. The predetermined at least one control device may be simply a predetermined one or a predetermined number of the normally functioning control devices, which may or may not be interchangeable with each other. If all of the mutually interchangeable control devices are abnormal, the control of the brake cannot be continued. If only one of the mutually interchangeable control devices is normal, on the other hand, it may be better not to stop or terminate the control of the brake. Although the control of the brake is possible as long as at least one of the control devices is normal, it may be better to stop the control from the standpoint of fail-safe protection of the braking system.
The control on/off device provided according to the above mode (7) may include a switch control device for turning off the switching device provided in the above modes (1) and (3) or the switching device provided in the above mode (4). In this case, the supply of the electric energy to the brake control apparatus or the electrically operated actuator is terminated by the switch control device of the control on/off device, to stop the operation of the braking system.
The control on/off device indicated above may be provided in the braking system according to a mode (24) described below wherein a controller switching device is provided between the electric power source device and the electrically operated actuator or the brake control apparatus such that the controller switching device and the power source switching device are connected in parallel with each other. In this case, the control on/off device may include a switch control device for holding the controller switching device in an on state when the predetermined at least one of the control devices is normal, and turning off the controller switching device when the predetermined at least one of the control devices is not normal.
(9) An electrically controlled braking system according to any one of the above modes (6)-(8), wherein the brake control apparatus includes an abnormality detecting device for detecting that at least one of the plurality of control devices is abnormal.
The abnormality detecting device may include a computer which is separate from the control devices described above with respect to the above modes (6)-(8), or may include at least one of those control devices. In the latter case, each of the control devices may have a mutually monitoring function, that is, may be adapted to check if any of the other control devices is abnormal. In this case, the abnormality detecting device may be provided without having to increase the required number of computers provided in the braking system.
Where the control devices are substantially identical with each other, the control commands generated by these control devices must be substantially identical with each other. In this case, the abnormality detecting device may be adapted to determine that the control devices are all normal, if the control commands generated by all of the control devices are substantially identical with each other, and determine that at least one of the control devices is abnormal, if the control commands are largely different from each other. The abnormality detecting device may be adapted to determine that if the control command or commands generated by at least one of the control devices is outside an optimum range, the at least one control device is abnormal. Where the control devices receive output signals of the same detectors as the input data on which the control commands are generated, the abnormality detecting device may use the input data to determine if each control device is normal or not. Where the control devices are different from each other, the abnormality detecting device may be adapted to determine if each control device is normal or not, depending upon whether the control commands generated by the control devices maintain a predetermined relationship.
Where the brake control apparatus includes at least three control devices, the diagnosis for abnormality of the control devices may be effected by decision by majority, or by comparing two or more sets of two output commands generated by the two control devices. Where the brake control apparatus includes two control devices, it may be difficult to check the control devices for abnormality, for instance, in the case where the control commands generated by the two control devices are both within an optimum range but are considerably different from each other. In this case, the brake control apparatus may include a primary control device and an auxiliary control device, so that the abnormality detecting device determines that the auxiliary control device is abnormal if the control commands generated by the primary and auxiliary control devices are considerably different from each other.
(10) An electrically controlled braking system according to the above mode (9), wherein each of the plurality of control devices includes a plurality of central processing units, and the abnormality detecting device includes a CPU abnormality detecting device for detecting that at least one of the plurality of central processing units is abnormal.
In the braking system according to the above mode (10), the CPU abnormality detecting device is adapted to detect that at least one of the central processing units included in one control device is abnormal. The CPU abnormality detecting device may include the central processing units. That is, the central processing units may serve as a part of the CPU abnormality detecting device. Alternatively, the CPU abnormality detecting device may include a computer separate from the central processing units. Where each control device includes two central processing units, these two units consist of a primary central processing unit and an auxiliary central processing unit.
Where the brake control apparatus includes xe2x80x9cnxe2x80x9d number of control devices each of which includes xe2x80x9cmxe2x80x9d number of central processing units, the brake control apparatus includes a total of xe2x80x9cnxe2x80x9dxc3x97xe2x80x9cmxe2x80x9d number of central processing units. Each of these xe2x80x9cnxe2x80x9dxc3x97xe2x80x9cmxe2x80x9d number of central processing units may have a mutually monitoring function so that these central processing units can be checked for abnormality, on the basis of results of their mutual monitoring functions. These results may be treated equally or given suitable different weights in determining the presence of abnormality of any one of the central processing units. The results of the mutually monitoring functions of all or selected combinations of the two central processing units may be used.
(11) An electrically controlled braking system according to any one of the above modes (1)-(5), wherein the brake control apparatus includes at least three control devices each of which is principally constituted by a computer.
In the braking system according to the above mode (11), all of the at least three control devices need not be connected to respective electric power sources. Namely, at least two of the at least three control devices may be connected to a single common electric power source. The present braking system may have any one of the technical features of the above modes (7)-(11).
(12) An electrically controlled braking system according to any one of the above modes (1)-(5), wherein the brake control apparatus includes at least one control device each of which is principally constituted by a computer, and the electric power source device includes a plurality of electric power sources which are arranged to supply electric energies to each of the at least one control device independently of each other.
Where a plurality of electric power sources are provided for a single control device, the control device is operable to control the operation of the electrically controlled brake, as long as at least one of the electric power sources is normal. The electric energies can be supplied from the plurality of electric power sources to the same control device, where the plurality of electric power sources are connected to the control device such that the electric power sources are connected in parallel with each other. The following mode (13) of the invention is one typical example of the above mode (12):
(13) An electrically controlled braking system according to any one of the above modes (1)-(12), wherein the electrically controlled brake includes a front brake for braking a front wheel and a rear brake for braking a rear wheel, and the brake control apparatus includes a front brake control device for controlling an operation of the front brake and a rear brake control device for controlling the rear brake, the electric power source device includes a plurality of electric power sources which are arranged to supply electric energies to the front brake control device independently of each other.
In the braking system according to the above mode (13), the electric energies are supplied from the two or more electric power sources to the front brake control device, so that the front brake control device is operable to control the operation of the front brake as long as at least one of the electric power sources is normal, even in the event of occurrence of an excessive output drop or other abnormality of at least one of the electric power sources.
For braking an automotive vehicle, the front wheel brake is more important than the rear wheel brake. In this sense, the above arrangement for supplying the electric energies from the two or more electric power sources to the front brake control device independently of each other is more effective than an arrangement for supplying the electric energies from the electric power sources to the rear brake control device.
The above form (13) of the invention is applicable to a braking system wherein the electrically controlled brake includes an electrically operated actuator, while the brake control apparatus includes an actuator control device for controlling the electric energy to be supplied to the actuator, as described above with the above form (3), and further includes a main control device for suppling the actuator control device with a control command indicative of the desired amount of electric energy to be supplied to the actuator or the desired braking force to be generated by the brake. In this case, the front brake control device and the rear brake control device may be included in either the main control device or the actuator control device.
(14) An electrically controlled braking system according to the above mode (13), wherein the rear brake includes a first rear brake and a second rear brake, and the rear brake control device includes a first rear brake control device for controlling the first rear brake and a second rear brake control device for controlling the second rear brake, the first rear brake control device being connected to one of the plurality of electric power sources while the second rear brake control device being connected to another of the plurality of electric power sources.
The first and second rear brake control devices indicated above are connected to the respective different electric power sources. These two electric power sources are two of the electric power sources which are arranged to supply the electric energies to the front brake control device independently of each other as described above with respect to the above mode (13).
(15) An electrically controlled braking system according to any one of the above modes (1)-(11), wherein the electrically controlled brake includes a front left brake for braking a front left wheel a front right brake for braking a front right wheel, a rear left brake for braking a rear left wheel and a rear right brake for braking a rear right brake, and the brake control apparatus includes a front left brake control device for controlling the front left brake, a front right brake control device for controlling the front right brake, a rear left brake control device for controlling the rear left brake and a rear right brake control device for controlling the rear right brake, the electric power source device including a front left brake power source and a front right brake power source which are arranged to supply electric energies to the front left and right brake control devices, respectively, independently of each other, and a common rear brake power source arranged to supply an electric energy to both of the rear left and right control devices.
(16) An electrically controlled braking system according to any one of the above modes (1)-(15), wherein the electrically controlled brake includes a rotor rotating with a front wheel, a friction member, and an electrically operated front brake actuator for forcing the friction member onto the friction member, and the electric power source device includes a plurality of electric power sources arranged to supply electric energies to the front brake actuator independently of each other.
In the braking system according to the above mode (16), the two or more electric power sources are provided for the front brake actuator, so that the front brake actuator is operable to control the brake for the front wheel, as long as at least one of the electric power sources is normal.
The relationship between the control devices and the electric power source device, which has been described above with respect to each of the above modes (12)-(15), is applicable to the relationship between the electrically operated actuator and the electric power source device. Examples of this application will be described with respect to the following modes (17) and (18) of the invention:
(17) An electrically controlled braking system according to the above mode (16), wherein the electrically controlled brake further two electrically operated rear brake actuators each of which is arranged to force a friction member onto a rotor rotating with a corresponding one of rear left and right wheels, and the electric power source device includes two electric power sources provided for the two rear brake actuators, respectively.
In the braking system according to the above mode (17), one electric power source is provided for each of the two rear brake actuators. The plurality of electric power sources provided for the front brake actuator may serve as these two electric power sources for the rear brake actuators. Alternatively, these two electric power sources for the rear brake actuators may be power sources different or separate from the power sources for the front brake actuator.
(18) An electrically controlled braking system according to any one of the above modes (1)-(17), wherein the electrically controlled brake includes an electrically operated front brake actuator for forcing a friction member onto a rotor rotating with a front wheel, and an electrically operated rear brake actuator for forcing a friction member onto a rotor rotating with a rear wheel, and the electric power source device includes a front brake power source for supplying an electric energy to the front brake actuator and a rear brake power source for supplying an electric energy to the rear brake actuator.
In the braking system according to the above mode (18), different electric power sources are provided for supplying electric energies to the front brake actuator and the rear brake actuator, respectively. This arrangement considerably reduces a risk that the front and rear brake actuators are both inoperable.
(19) An electrically controlled braking system according to any one of the above modes (1)-(18), wherein the electrically controlled brake includes a plurality of brakes for braking respective wheels of the automotive vehicle, the brakes including respective electrically operated electric motors each of which is arranged to force a friction member onto a rotor rotating with a corresponding one of the wheels, the braking system further comprising a plurality of actuator switching devices each of which is disposed between the electric power source device and a corresponding one of the electric motors, each of the actuator switching devices being operable between a connecting state for connecting the electric power source device to the corresponding electric motor, and a disconnecting state for disconnecting the electric power source device from the corresponding electric motor.
In the braking system according to the above mode (19) wherein the actuator switching devices are provided for the respective electric motors, each of the electric motors can be connected and disconnected to and from the electric power source device. For example, each actuator switching device may be adapted to be brought into its disconnecting state when the corresponding electric motor becomes abnormal. In this case, the actuator switching devices corresponding to the normal electric motors are held in the connecting state to hold the normal electric motors operable, while only the abnormal electric motor is held at rest, so that the brakes corresponding to the normal electric motors can be activated or held in operation. Thus, an occurrence of abnormality of some of the electric motors will not cause all of the electric motors to be inoperable. The actuator switching devices may be adapted to be switched to the disconnecting state when the corresponding motor control devices or motor driver circuits become abnormal. The motor control devices, which are part of the brake control apparatus, are arranged to control the electric energies to be supplied to the respective electric motors.
Where the plurality of electric motors are connected to the electric power source device such that the electric motors are connected in parallel with each other, the actuator switching devices are provided in respective circuits corresponding to the electric motors.
(20) An electrically controlled braking system according to the above mode (19), wherein the brake control apparatus includes motor control devices for controlling the electric motors, respectively, and each of the plurality of actuator switching devices includes two switches connected in series with each other, one of the two switches of the each actuator switching devices being turned off when the corresponding electric motor becomes abnormal, the other of the two switches being turned of f when the corresponding motor control device becomes abnormal.
In the braking system according to the above mode (20), each actuator switching device is placed in its disconnecting state when at least one of the corresponding electric motor and motor control device becomes abnormal or defective.
(21) An electrically controlled braking system according to any one of the above modes (1)-(20), wherein the electrically controlled brake includes a rotor rotating with the wheel, a friction member, and an electrically operated actuator for forcing the friction member onto the rotor, and the brake control apparatus includes a main control device which determines a physical quantity relating to a desired value of a braking force to be produced by the brake and generates a control command representative of the determined physical quantity, and an actuator control device which controls the electrically operated actuator according to the control command and generates a signal representative of a physical quantity relating to an actual value of the braking force produced by the brake.
In the braking system according to the above mode (21), data communication is effected between the main control device and the actuator control device, so that the control command representative of the desired braking force is fed from the main control device to the actuator control device, while the signal representative of the actual braking force is fed from the actuator control device to the main control device. The physical quantity relating to the desired braking force may be the desired value of the braking force per se, or an amount of electric current to be supplied to the actuator so as to permit the brake to produce the desired braking force. The physical quantity relating to the actual braking force may be the actual value of the produced braking force, a force by which the friction member is forced onto the rotor, or a physical quantity representing a load acting on the actuator ((e.g., an electric current flowing through the actuator).
(22) An electrically controlled braking system according to the above mode (21), wherein the actuator control device is spaced from the main control device and disposed on a sprung member of the automotive vehicle such that the actuator control device is located near the actuator, the main control device and the actuator control device have means for data communication therebetween through a local area network (LAN).
If the main control device and the actuator control device are arranged integrally with each other, the data communication between these devices can be effected with high efficiency and reliability. However, the integral arrangement requires an increased memory capacity and an increased number of input and output ports, resulting in an increase in the overall cost of manufacture of the brake control apparatus.
Where the main control device and the actuator control device are separate and spaced from each other, a comparatively long time is required for the data communication between these control devices, leading to a delay in controlling the electrically controlled brake. It is also noted that the electrically operated actuator and the actuator control device are desirably arranged integrally with each other, since the actuator is controlled by control commands received from the actuator control device. The actuator is disposed on an unsprung member of the vehicle. If the actuator control device is also disposed on the unsprung member with the actuator, the actuator control device is undesirably subject to vibrations of a relatively large amplitude. In view of the above, the braking system according to the above mode (22) is arranged such that the actuator control device is disposed on a sprung member of the automotive vehicle and is located near the actuator, and such that the data communication between the main control device and the actuator control device is effected through a local area network (LAN), so-called xe2x80x9ccar area network: CANxe2x80x9d. The data communication through the CAN permits efficient multiple communication, that is, transmission and reception of large volume of information in a short time, between the main control device and the actuator control device, without a control delay. Since these two control devices are both disposed on the sprung members of the vehicle, they are less likely to be influenced by noises, and are protected from large-amplitude vibrations.
(23) An electrically controlled braking system according to the above mode (21) or (22), wherein the main control device includes an abnormality detecting device for detecting an abnormality of the actuator control device, on the basis of the signal representative of the physical quantity relating to the actual value of the braking force produced by the brake.
If the physical quantity relating to the actual braking force is outside a predetermined range, the actuator control device which generated the signal representative of this physical value is considered to be abnormal. The abnormality detecting device may be adapted to detect an abnormality of the actuator control device, on the basis of the physical quantity relating to the desired braking force determined by the main control device, as well as the physical quantity relating to the actual braking force. Namely, the abnormality detecting device may be adapted to determine that the actuator control device is abnormal, if the difference between those two physical quantities exceeds a predetermined value. The abnormality detecting device is particularly effective where it is provided together with the actuator switching device which has been described above with respect to the above modes (19) and (20).
(24) An electrically controlled braking system according to any one of the above modes (1)-(23), wherein the electrically controlled brake includes a rotor rotating with the wheel, a friction member, and an electrically operated actuator for forcing the friction member onto the rotor, the braking system comprising an electric circuit in which the actuator and the brake control apparatus are connected to the electric power source device such that the actuator and the brake control apparatus are connected in parallel with each other, and wherein the switching device is disposed in a common portion of the electric circuit which serves to connect the electric power source device to both of the actuator and the brake control apparatus.
(25) An electrically controlled braking system according to the above mode (24), further comprising a controller switching device which is turned off to disconnect the brake control apparatus from the electric power source device when the brake control apparatus is abnormal, the controller switching device being disposed in an exclusive portion of the electric circuit which serves to connect the electric power source device to only the actuator.
In the braking system according to the above mode (25), the electric power source device, the power source switching device, the controller switching device and the electrically operated actuator are connected in series with each other. Even when the power source switching device is in the on state, an electric energy is not supplied to the actuator if the controller switching device is in the of f state.
Where the electrically controlled brake includes a plurality of electrically operated actuators, a group of these actuators and the brake control apparatus are connected to the electric power source device such that the group of actuators and the brake control apparatus are connected in parallel with each other, and the actuators are connected in parallel with each other through respective parts of the above-indicated exclusive portion of the electric circuit which serves to connect the electric power source device to the group of actuators. In this case, the controller switching device for each actuator is disposed at a position in the above-indicated exclusive portion of the electric circuit, which is between the electric power source device and the end of each of the above-indicated respective parts, which end is remote from the corresponding actuator. The actuator switching device for each actuator is disposed in the corresponding one of the above-indicated parts of the electric circuit through which the actuators are connected in parallel with each other.
(26) An electrically controlled braking system according to the above mode (25), wherein the controller switching device includes a plurality of switches connected in parallel with each other, and the brake control apparatus includes a plurality of control devices which are principally constituted by respective computers and which correspond to the plurality of switches, respectively, and a switch control device for turning off one of the plurality of switches of the controller switching device when one of the control devices which corresponds to the one of the plurality of switches becomes abnormal.
Where the controller switching device includes two switches and the brake control apparatus includes two control devices, one of the two switches is turned off by the switch control device when one of the control devices which corresponds to the above-indicated one switch becomes abnormal. The controller switching device is held in the on state as long as at least one of the control devices is normal, and is brought into the off state when all of the control devices are abnormal.
(27) An electrically controlled braking system according to any one of the above modes (24)-(26), wherein the electric power source device includes a plurality of electric power sources, and the switching device includes a main switch provided in the common portion of the electric circuit which includes one of the electric power sources, a plurality of coils which are energized and de-energized to turn on and of f the main switch, a plurality of coil connecting circuits for connecting the plurality of coils to the plurality of electric power sources, and a plurality of brake switches which are respectively provided in the coil connecting circuits and which are turned on when the brake operating member is operated.
In the braking system according to the above mode (27), the main switch of the switching device is turned on to connect the electric power source device to said brake control apparatus when at least one of the plurality of coils is energized. The coils are connected to the respective electric power sources. Accordingly, the main switch can be turned on as long as at least one of the electric power sources is normal. Thus, the present arrangement reduces a probability that the main switch cannot be turned on.
(28) An electrically controlled braking system according to any one of the above modes (24)-(26), wherein the electric power source device includes a plurality of electric power sources, and the electrically controlled brake includes a plurality of electrically operated actuators, the brake control apparatus including a plurality of actuator control devices for controlling the plurality of actuators, respectively, the braking system comprising a plurality of electric circuits each of which includes a corresponding one of the electric power sources, a corresponding one of the actuators and a corresponding one of the actuator control devices, the switching device including a main switch provided in each of the plurality of electric circuits, a coil which is energized and de-energized to turn on and off the main switch, a coil connecting circuit for connecting the coil to the corresponding one of the electric power sources, and a brake switch which is provided in the coil connecting circuit and which is turned on when the brake operating member is operated.
The braking system according to the above mode (28) has a plurality of electric circuits including respective electric power sources. In the event of an excessive output drop or other abnormality of one of the electric power sources, the corresponding main switch is not turned on even when the brake operating member is operated. In this event, however, the main switch or switches corresponding to the normal electric power source or sources can be turned on when the brake operating member is operated.
(29) An electrically controlled brake system according to any one of the above modes (1)-(28), further including an mechanically operated brake mechanically operated by the brake operating member, and wherein the brake control apparatus includes a switching mechanism operable between a connecting state in which an operating force-applied to the brake operating member upon operation of the brake operating member is transmitted to the mechanically operated brake and a disconnecting state in which the operating force is not transmitted to the mechanically operated brake, the brake control apparatus further including a switching control device which is normally placed in the disconnecting state, and is brought into the connecting state when an electrical abnormality of the electrically braking system takes place.
In the braking system according to the above mode (29), the mechanically operated brake is not activated upon operation of the brake operating member, while the switching mechanism is placed in the disconnecting state. When the brake operating member is operated while the switching mechanism is placed in the connecting state, the mechanically operated brake is activated to brake the vehicle wheel. The switching control device may be adapted to bring the switching mechanism into the connecting state when the electric power source device or the brake control apparatus becomes abnormal, for example. According to this arrangement, the mechanically operated brake can be activated by operation of the brake operating member even while the braking system is electrically abnormal.
The technical feature of the above mode (29) is available independently of the technical feature of any one of the above modes (1)-(28).
(30) An electrically controlled braking system for braking a front wheel and a rear wheel of an automotive vehicle, comprising: a front wheel brake (10, 12) including a rotor rotating with said front wheel, a friction member, and an electrically operated actuator for forcing the friction member onto the rotor, for thereby braking the front wheel; a plurality of electric power sources arranged to supply electric energies to the front wheel brake independently of each other; and a brake control device for controlling the electric energy to be supplied from at least one of the electric power sources to the electrically operated actuator of the front wheel brake, to thereby control an operation of the front wheel brake.
(31) An electrically controlled braking system for braking a plurality of wheels of an automotive vehicle, by operations of respective electrically operated actuators, wherein an actuator switching device is provided between each of the electrically operated actuators and one electric power source for driving each actuator, such that the actuator switching device is operable between a connecting state for connecting each actuator and the electric power source to each other, and a disconnecting state for disconnecting each actuator and the electric power source from each other.